What's The Objective-c Equivalent Of Js's `map()` Function?
Solution 1:
You can use NSArray
's enumerateObjectsUsingBlock:
if you're on OS X 10.6 or iOS 4.:
NSMutableArray *mapped = [NSMutableArray arrayWithCapacity:[array count]];
[array enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
id mapObj = DoSomethingToObject(obj);
[mapped addObject:mapObj];
}];
Solution 2:
It depends. If you have, say, an array of objects, and these objects have a URL
property (for example), then you can do:
NSArray * urls = [myArray valueForKey:@"URL"];
Likewise, if you can trigger the behavior of the objects in question via a single message that takes 0 or 1 parameters, you can do:
[myArray makeObjectsPerformSelector:@selector(doFoo)];
//or:
[myArray makeObjectsPerformSelector:@selector(doFooWithBar:) withObject:aBar];
For anything beyond that, you'll have to iterate over the objects yourself. You can use a for()
loop, a for(in)
loop, or something like -enumerateObjectsUsingBlock:
, etc.
Solution 3:
You do it yourself. There is no single method equivalent to what you want.
Edit: For those downvoting, this was the correct answer at the time (three years ago) and still is for Objective-C, but Swift does have a map()
function.
Solution 4:
Check BlocksKit, it provides map, reduce and filer for NSArray.
- (NSArray *)map:(BKTransformBlock)block;
- (id)reduce:(id)initial withBlock:(BKAccumulationBlock)block;
- (NSArray *)select:(BKValidationBlock)block;
Solution 5:
Category function for NSArray an alternative
- (NSArray *)map:(id(^)(id, BOOL *))block {
NSMutableArray * array = [NSMutableArray array];
[self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
id newObject = block(obj,stop);
if (newObject == nil) {
newObject = [NSNull null];
}
[array addObject:newObject];
}];
return array.copy;
}
Category function for NSMutableArray an alternative
- (NSMutableArray *)map:(id(^)(id))block {
NSEnumerator * enumerator = ((NSArray *)self.copy).objectEnumerator;
id obj; NSUInteger idx = 0;
while ((obj = enumerator.nextObject)) {
self[idx] = block(obj) ?: [NSNull null];
idx++;
}
returnself;
}
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